Spatial contrast sensitivity was used to assess losses or changes in overall visual resolution in patients having a variety of toxic, inflammatory, degenerative, or congenital retinal and neuro-ophthalmological disorders of the visual system. A criterion-free forced-choice psychophysical procedure was used throughout, since this method was found to produce minimal false positive or false negative diagnoses at initial test and to minimize spurious changes in sensitivity with repeated testing. For detecting early loses and monitoring changes in central-field visual resolution, this test continued to be superior to conventional visual acuity testing.